The primary objective of this epidemiologic study is to focus on the potential value of strength and flexibility as contributors to musculoskeletal health in sedentary and physically active adults. Musculoskeletal health is broadly defined as the avoidance of musculoskeletal (bone, tendon, muscle and joint) disorders and the ability to perform occupational, recreational, household and self care tasks. Two specific aims will be addressed using approximately 12,000 adult male and female subjects who performed a strength and flexibility assessment as part of a comprehensive preventive medicine evaluation. The first specific aim relates to the descriptive epidemiology of strength and flexibility, and is to: a. establish age, sex and weight adjusted percentile rankings for strength and flexibility measures in adults without acute or chronic musculoskeletal disorders; b. investigate the inter- relationships between these measures; and c. determine the reproducibility of these measures. The second specific aim is to determine the association of baseline strength and flexibility to: a. the risk of subsequently (follow up = 3-10 years) developing musculoskeletal disorders; and b. subsequent functional capability as evidenced by the reported ability to perform occupational, recreational, household and self care tasks. Musculoskeletal disorders and functional capability will be evaluated by means of a mail survey. The strengths of the proposed research include the extensive existing database, the magnitude of follow-up, the suitability of available subject population, the expertise of the research team in conducting such a study, and its highly cost- efficient nature. Our study will constitute an important contribution to the elucidation of the descriptive epidemiology of strength and flexibility, and the precise role that these fitness attributes play in the promotion of musculoskeletal health in adults.